This invention relates to ring binder mechanisms, and more particularly, to a clinch fastener for securing a ring metal of the ring binder mechanism to a spine portion of a binder.
Ring binder mechanisms use a ring metal assembly employing binder rings openable for the insertion and removal of material such as hole-punched sheets of paper, and a lever mechanism by which the rings are opened and closed. A plate covering the lever mechanism usually includes provisions at each end for attachment of the ring metal to a spine section of the binder. One form of attachment includes rivets secured to the binder and passing upward, through the ring metal. For cosmetic purposes, it is desirable to use a fastener for securing the ring binder mechanism to the binder which is not visible on the exterior surfaces of the binder. U.S. Pat. No. 5,755,513 to To, U.S. Pat. No. 5,160,209 to Schuessler, and U.S. Pat. No. 5,100,253 to Cooper each illustrate a fastener comprising an upright rivet structure mounted on a rectangular attachment plate and having a number of prongs adapted to grip an interior surface of a binder. The rivet structures in each of these patents are designed to pass through openings in the binder mechanism for attachment thereto. Prongs on the other end of the fastener then allow the ring metal/fastener subassembly to be attached to the binder spine by a pressing operation or the like.
While useful for their intended purpose, previous fastener designs have several drawbacks. For example, each fastener has a rectangular plate from which prongs are punched directly. As a result, there is more metal surrounding some prongs than others, meaning some areas of the fastener are weaker than others. Also, the rectangular configuration hinders automated assembly of the binders because fasteners must be oriented such that the longest dimension of the attachment plate is aligned along the spine of the binder.
Finally, all of these prior art fasteners require a preformed rivet or eyelet structure in order to locate the fastener in a corresponding opening in the ring metal, and secure the fastener to the ring metal by a punching or spinning operation by which an end of the rivet or eyelet is deformed about the opening to attach one end of the fastener to the ring metal. Further, the upright rivet structure used in these prior art fasteners has either a shoulder incorporated into the rivet structure itself, as is shown in the '513 patent, or requires a separate support to hold the ring metal in position as the upper surface of the rivet is deformed to secure the ring metal, as is seen in the '209 and '253 patents. Such construction adds to the overall cost of the fastener